1. Field of the Invention
The present invention relates to an unloader with vertical screw conveyers which is capable of providing a plurality of conveyance routes for unloading a plurality of different kinds of bulk commodities, such as coal and wheat.
2. Description of the Prior Art
A conventional unloader with a vertical screw conveyer is shown in FIG. 12. As shown in FIG. 12, in such a conventional unloader, a boom 1' has a single boom conveyer 11', and a single vertical screw conveyer 4' having a chute facing the conveyer 11' is hung from the head of the boom 1' Accordingly, this unloader provides only one conveyance route formed by the screw conveyer 14', the chute, the boom conveyer 11', another chute 20' and a conveyer 21' on the ground. In consequence, if a single unloader of this type is used to unload a plurality of different kinds of bulk commodities, each time the kind of bulk commodity to be unloaded changes, the entire conveyance route has to be cleaned with water or by another suitable method, in order to remove any of the previously unloaded bulk commodity which might otherwise remain along the conveyance route and mix with the subsequent bulk commodity. Because such cleaning takes a long time, a quick changeover in the kind of bulk commodity being unloaded is hindered, thus lowering the efficiency of unloading.